In the field of respiratory devices, nebulizers are important devices used for the inhalation of drugs in the form of an aerosol. A nebulizer employs an apparatus that generates an aerosol or mist from a solution (usually an aqueous solution) or suspension of a drug. The mist may be an aerosolized suspension or an atomized suspension of drug, meaning micro-droplets suspended in air, medical oxygen, or other inhalable gas. The aerosol is conveyed to the mouth and/or nose of a patient and inhaled into the lungs. In some cases, the mist is conveyed to the lungs through a mouthpiece. In other cases, the nebulizer may be coupled to an inhalation mask.
Nebulizers operate by passing a stream of air or other suitable gas, such as medical oxygen, over or through a reservoir holding an aqueous solution of a drug for inhalation. In many cases, a stream of pressurized gas enters the nebulizer through a gas inlet and through a jet to produce a Venturi effect that draws a stream of the solution through a narrow passage or capillary from a pressure differential, whereby the liquid enters the jet and becomes atomized. Typically, a baffle is employed in the jet effluent that prevents large droplets from exiting the device, so that only aerosol micro-droplets of drug containing solution exit the device. An example of such a nebulizer is disclosed in U.S. Pat. No. 4,588,129. The aerosol is then inhaled by the patient. Typically, the aerosol production is continuous, so a vent is typically provided to ensure that the pressure differential created by the jet operates continuously and consistently.
The drug reservoir in nebulizers is usually a cone, cup, or bowl-shaped vessel into which a sterile aqueous solution of the drug is added. Accordingly, the orientation of the nebulizer is important, and the device must be kept approximately in an orientation such that the drug-containing solution stays in the reservoir where it can be aerosolized in the nebulizer. This restricts the range of motion available to the patient and nebulizer during use.
Typical drugs used with nebulizers are drugs for the treatment of asthma and obstructive pulmonary diseases, but other pulmonary and systematic medications may be administered by inhalation with nebulizers. For example, albuterol (called salbutamol in many countries), used for treating asthma and bronchospasm, may be administered as a nebulized solution. Another example is pentamidine, a drug used to treat Pneumocystis pneumonia (PCP).
Nebulizers are particularly useful for the administration of inhaled drugs to small children, elderly, unconscious, or disabled patients who cannot coordinate their breathing or take instruction on the use of coordinated inhalation devices, such as a metered dose inhaler. With a nebulizer, the dose of drug is administered to the patient over a period of several minutes, and possibly ten to twenty (or more) tidal or slow deep inhalations per minute, so breathing coordination is not required.
In the case of patients who cannot hold a mouthpiece in their mouth, an inhalation mask may be used with a nebulizer. This creates a complication in that the orientation of the mask and the nebulizer apparatus is important, to maintain the drug-containing solution in the reservoir for nebulization. Most nebulizer masks currently on the market have relatively inflexible connectors from the mask to the nebulizer apparatus and typically have a corrugated tube with a fixed 90° elbow for connection to a nebulizer. This requires that the patient inhale the mist while sitting straight in order to keep the nebulizer approximately vertical to avoid spilling the drug solution in the nebulizer or having the solution flow away from the capillary that carries the drug to the air-jet of the Venturi.